#include<bits/stdc++.h>
using namespace std;
int main(){
	int n;
	while(cin>>n){
		if(n>100 || n < 0){
			cout<<"Score is error!" ;
		}else{
			if(n >= 90){
				cout<< "A";
			}else if( n >= 80){
				cout<< "B";
			}else if( n >= 70){
				cout << "C";
			}else if( n >= 60){
				cout << "D";
			}else{
				cout << "E";
			}
			
		}
		cout<<endl;
		
	}
	return 0;
}
